This invention relates to grate construction for a fixed bed coal gasifier.
In the fixed bed coal gasification process, coal enters the gasifier at the top and lands on top of the charge of coal already in the gasifier where it receives heat from the upwardly-moving product gas. As the combustion process near the bottom of the gasifier (above the grate) consumes some of the coal and the rest of the coal is gasified, coal at the top of the charge gradually moves down, passing through a series of treatment stages: initial heating; devolatilization and coking; gasification, and carbon oxidation. A large number of chemical reactions occur and a minimum temperature of about 1700- 1900.degree. F is required. Usually the gasification is conducted under superatmospheric pressure. When air and steam are introduced to the combustion zone, the end product is producer gas; when oxygen and steam are employed, the end product is synthesis gas.
It is well recognized in the coal gasification art that problems in the operation of coal gasifiers often result from large agglomerates or clinkers, which retard the solids flow through the grate and ash collection-and-discharge assembly therebelow. This can shut down the gasifier. Heretofore known grate constructions have been complex, inefficient and expensive and not entirely satisfactory from the standpoint of such solids flow retardation and gasifier shutdowns.
It has now been found by practice of the present invention that clinker problems can be effectively overcome by a grate construction adapted to substantially reduce the size of large solids, e.g. clinkers, received thereon.